The current Internet Protocol (IP) technologies have increasingly high requirements on the quality of service (QoS), for example, the voice over IP (VOIP) or IP television (IPTV) emphasizes a highly efficient service of a low delay, low jitter, and no packet loss. In order to satisfy the demands of end users, operators require the network devices to provide an excellent forwarding capability, which naturally imposes higher requirements on equipment suppliers.
When a network device fails or a physical link failure occurs in a terminal, the forwarding capability of the node or the link is lost, and the provided service is inevitably influenced to some extent. For an IP (Internet) phone, the influence on a user experience is disconnection. For an IPTV, the influence on the user experience is a pause of the program. Therefore, how to minimize the influence and improve the user experience becomes a technical problem to be solved urgently.
Taking a video service provided by the IPTV as an example, if the time for influencing the service is controlled to be approximately 50 milliseconds (ms) to 100 ms, the lost data is quite limited. Thus, the human eyes nearly cannot distinguish the difference, and no greater influence occurs. However, if the time for influencing the service reaches 5 seconds (s) to 10 s or even an interruption at a minute level occurs, the user possibly cannot endure a picture interruption for a long time, thereby influencing a user satisfaction rating on the service.
The IPTV needs to send data to a great number of users simultaneously from a video server, such that the forwarding operation needs to be optimized by using a multicast technology in a backbone network. Referring to FIG. 1, the server only sends a video traffic without setting up a great number of links with the users, and the network device replicates the traffic at points (cross-points) that need the replication.
A solution of processing a network failure in a conventional IP multicast technology is given as follows.
Referring to FIG. 2, firstly, a video traffic from a video server to a receiver reaches the receiver on the end of the network through RT1, RT2, and RT3. When RT2 fails due to certain reasons, firstly, the unicast routing protocol detects a change of the network topology, and reselects a path RT1, RT4, and RT3. Then, a multicast protocol depending on unicast starts to select a new path to forward the traffic. As the multicast is based on “reverse path forwarding (RPF)”, RT3 initiates a traffic request to RT4, RT4 sends the traffic request to RT1, RT1 adds a new egress port for the traffic, and then the traffic is enabled to be forwarded to the receiver through the new path RT1, RT4, and RT3.
The time required from the occurrence of the failure to the traffic restoring equals the time required for finding out the topology change by the unicast routing protocol, plus the time required for re-calculating a path, plus the time required for initiating a traffic request by the multicast, plus the time required for adding an egress port by an upstream node. In the conventional art, even if the utmost possible optimization is performed, the total time at least reaches a second level, which causes a severe influence on the user experience. Therefore, the current IP multicast technique can only correctly replicate the traffic, but cannot satisfy the high quality and highly efficient routing demands.
Referring to FIG. 3, the multi-protocol label switching (MPLS) tunnel technology based on the unicast has been widely applied, so that all the technical solutions in the conventional art can only protect the point-to-point services, such that the applications thereof are restricted.
To sum up, the solution for processing the network failure in the conventional art can only protect the point-to-point unicast services, such that the applications thereof are rather limited. Furthermore, if the network failure occurs in the multicast service, only the traffic can be correctly replicated, but the high quality and highly efficient routing demands cannot be satisfied.